My most common responses to questions in AD forums.

I don't know why, but for whatever reason I quote the following few KB articles/links/mantras almost every single day:

"Did you do a metadata cleanup on that b0rked DC you're describing?"

• http://www.petri.co.il/delete_failed_dcs_from_ad.htm
• http://support.microsoft.com/kb/216498

"'net time' is a deprecated method.  Please see the following to configure time in your AD domain:"

• http://support.microsoft.com/kb/816042

"The Global Catalog/Infrastructure Master MCSE-exam guide cautionary tale is a moot point in a single-domain environment."

"There's this thing called 'adminSDHolder' that's making your permissions 'disappear'. Stop making your normal users Domain Admins/Administrators/whatever and give them separate elevated accounts."

• http://msmvps.com/blogs/ulfbsimonweidner/archive/2005/05/29/49659.aspx

"Schema update from 2000 to 2003 R2 isn't working, huh?  Did you use Disc 2? No?  Go use Disc 2, you'll be fine now."

Beyond that, I probably get something involving the words "USN rollback" and "invocationID" once a month; though more often than not anymore that's happening as a result of "restoring" a DC using GHOST rather than a DC staying offline beyond the Tombstone Lifetime.

My other favourites involve the following 2 phrases:

• "Exchange on a DC? Are you mental?", and...
• "No, you can't let someone log on locally to a 2003 DC without making them the security-equivalent to a DA. You may think you can, but you just plain can't."